In general, a flywheel is disposed between an engine and a transmission in order to prevent torsional vibration generated in a crankshaft of the engine. Recently, a dual mass flywheel having a wide damping area has been gradually used in order to reduce noise, vibration, hastiness (N.V.H).
In general, a dual mass flywheel includes a primary wheel 1 connected to a crankshaft, an arcspring 2 included in the primary wheel 1, a flange 3 for receiving rotator power of the crankshaft from the arcspring 2, and a secondary wheel (not shown) secured to the flange 3, as shown in FIG. 1.
According to rotation of an engine, torque is transmitted to the flange 3 and the secondary wheel and the flange 3 and the secondary wheel rotate. The flange 3 compresses the arcspring 2 and compression and tension of the arcspring 2 are repeated according to torque change.
The arcspring 2 needs to be designed to have appropriate a stiffness for an engine torque. This is because a region A of a graph of FIG. 1 is an operating region of the arcspring 2 and the operating region is affected by the stiffness of the arcspring 2.
In particular, coils of the arcspring 2 contact each other and thus the arcspring 2 reaches a limit at which the arcspring 2 is not capable of being compressed any more. In this case, the applied torque is referred to as an end torque.
According to a driving condition, a sharply high torque may be generated. In this regard, when torque reaches the end torque at which the arcspring 2 is not capable of being compressed any more over an operating region of the arcspring 2, an impact is generated to excessively impact coils of the arcspring 2 on each other, and in this case, the arcspring 2 is damaged due to the impact (refer to FIG. 2).